The Mandarin Oriental website does have a space for "Corp/Promo Code". So, your first step would be to contact the person/department at your company who handles your travel program. That's the only way to determine if you have access to a corporate code.

Typically, the government rate would be conferred through your employment. So, ask the same person at your workplace.

As for other discounts, I'll leave that to other members. Although, high end hotels aren't usually known for offering deep discounts to the general public. They usually don't have to.